As far as I have been able to determine, the anecdote that started this thread - that that the "volcanic bubble" under Yellowstone's basin has raised over 100 feet in the past day and there are indications it is ready to blow - is false.
The movement of this "bubble" - do they mean the dome under the lake, or the magma far below the dome? - would be accompanied by earthquakes. It would not arrive "as a thief in the night," to coin a phrase.
Yet -- an interesting thing about "unimaginable" events is that they remain "unimaginable" up until the very moment they occur.
Did anyone ever thing they would see something as "exotic" as a volcano inside the lower 48 states blowing itself up? What a wacky idea!
Until May 18, 1980... and twenty one times since then.
Did any of us ever think we would see a passenger airliner fly into one of the largest buildings in the world? Why, that would be CRAZY!
Not unitl 9/11/2001, when we saw it happen twice.
Of course we can't imagine yellowstone blowing up during our lifetimes, and we find it hard to imagine that it could blow up anytime in the foreseeable future - the next 10,000 years of so.
Yellowstone has blown up in the past. There is no Cosmic Bomb Squad to defuse the yellowstone hot spot, so we know it is going to blow up again someday. The geological record suggests an interval of about 600K years between explosions. The last explosion was about 600K years ago. The magnitude of those past eruptions exceeds anything in past human experience.
Yes, the "fudge factor" is large - maybe as much as 100K years.
On the other hand, WHAT IF we discovered that the Yellowstone Volcano had erupted INVISIBLY 25 years ago?
Yeah... that's the ticket!